Ultra-Lightweight Cement Slurry to Seal Wellbore of Poor Wellbore Stability

Abstract

The article presents the recipe for ultra-lightweight cement slurry for wellbore sealing. In ordinary lightweight cement slurries, the addition of microspheres and a large amount of water are used to maintain rheological parameters. This is a problem because the light particles of microspheres segregate. The cement sheath from such a cement slurry has an anisotropic microstructure and does not stabilize the casing column. In the new ultra-light cement slurry, 60% aluminosilicate microspheres and a large amount of water were used. The ultra-light weight slurry has a density below 1.2 g/cm3. This cement slurry does not segregates and in the sedimentation stability test has the same density at all measuring points. The cement slurry, despite the larger amount of water, has the same filtration as the control sample. The technological parameters of the slurry are adapted to the borehole conditions. Cement slurry is a ready-made application to seal a borehole with poor wellbore stability under conditions of 40 °C and 10 MPa pressure. The cement sheath structure in the wellbore after binding is homogeneous. The use of such slurry allows to reduce the risk of wall damage in wellbores of poor stability.